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+6V
KABOl-
K
S
M
K
L.
-f
fiV
KDB05-
A6247
MASK
FLIP
FLOP
Figure
2-14.
SMKl
Using
Bit
5
to
Control
Mask
Flip-
Flop
STL
-
Stall
Instruction
Although
the
hardware
for the
stall
instruction
is
quite
simple,
the
application
may
be
varied.
In
the
example
in
Figure 2-15
when
the
program
needs
to
synchronize with
the
exter-
nal
system
clock, the
controller resets
the flip-flop
by separate
programming
action
and
then
executes an
STL
instruction.
When
the
system
clock
drops
from +6V
to
ground,
the flip-flop
sets,
and
the
stall
breaks.
+6V
KSTAL-
J
_L
RESET
PULSE
FROM PROGRAM
Figure
2-15.
STL
Gating
INTERRUPTS
An
external device
may
create a
program
interrupt
to
request
a
data transfer or
to
inform
the
program
of
an
event
in the
external
system.
The
external device activates
the
interrupt by
grounding
interrupt
line
KINTL-.
All
devices share
this line,
therefore,
in
cases
of
simultaneous
interrupts,
more
than
one device
may
ground
the
line.
A
device
must
keep
KINTL-
at
ground
until
the
program
informs
the
device
that
its
particular
inter-
rupt has
been
recognized.
2-17
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